The present invention relates to a polymer useful as a photoresist in a lithographic process for fabricating a semiconductor device, and a method of forming a micro pattern using the same. More specifically, the present invention relates to a polymer which can be used in a photoresist composition for forming an ultra-micro pattern in the manufacture of 4G and 16G DRAM semiconductor chips using short wavelength light sources, such as KrF (248 mn), ArF (193 nm), an E-beam, or an ion-beam. The polymer of the present invention is particularity useful in a photoresist composition for the top surface image (TSI) process using silylation.
In the manufacturing process of a semiconductor element, a photoresist is generally used to form a pattern with a fixed form on a semiconductor element. To obtain the desired photoresist pattern, a photoresist solution is coated on a surface of a semiconductor wafer, the coated photoresist is exposed to patterned light, and then the wafer undergoes a developing process. As a result, a photoresist pattern is formed on the wafer.
If the photoresist pattern is manufactured using a conventional silylation process, the photoresist is usually composed of diazonaphtoquinones compounds and a novolac resin, or a photo acid generator and polyvinyl phenol resin. When the photoresist resin is exposed to the patterned light source (e.g. ArF, KrF, or I line) and then baked, an alcohol group (R--O--H) is formed in the resin at the exposed regions. After baking, the photoresist resin is silylated with a silylation agent such as hexamethyl disilazane or tetramethyl disilazane. In the silylation process, an N--Si bond is first formed, but since the N--Si bond is weak, it then reacts with the R--O--H group in the photoresist polymer to form a R--O--Si bond. The photoresist resin with bonded silicon atoms then undergoes a dry developing using O.sub.2 plasma to form a silicon oxide film. The lower portions of the silicon oxide film remain even after the development of the photoresist and as a result, the desired pattern is formed.
The above-described silylation process for forming a photoresist pattern has several deficiencies when it is used with shorter wavelength radiation. In particular, when a KrF eximer laser is used as the light source to expose known photoresist polymers, it is impossible to form an ultra-micro pattern less than 0.10 .mu.m L/S using the silylation process. When an ArF light source is used, the lens of the exposer can be damaged due to the high energy level of the ArF light. Therefore, the photoresist must be exposed to a lower amount of energy, for example, less than 10 mJ/cm.sup.2. If the photoresist is not exposed sufficiently to this lower energy, the desired pattern is not formed.